1. Field of the Invention
The present invention relates generally to swabbing structures and methods of use for assaying purposes. More particularly, the invention relates swabbing structures for collecting analyte from a test surface and conducting an assay in a light-tight environment to efficiently detect and quantify low level luminescent emissions, which are proportional to the volume of analyte collected from the test surface.
2. Description of the Prior Art
Hitherto, a number of techniques and arrangements have been proposed that employ xe2x80x98luciferase-luciferin reactionsxe2x80x99 to assay and quantify a specimen or a volume of analyte. As is well known, luciferase-luciferin reactions involve the measurement of adenosine triphosphate (ATP), a material central to metabolism in virtually all living cells. As ATP is necessary for all living organisms to function, it serves as an excellent marker to indicate the presence of living matter (e.g., bacterial and other microbial matter). Accordingly, if one can ascertain with a reasonable accuracy a quantity of ATP present in a sample or specimen, either through direct or indirect measurement, one can make a determination of the quantity of microbes, microbial matter, or more generally the amount of xe2x80x98analytexe2x80x99 present. A most preferred indirect method of measuring and quantifying a volume of analyte is by determining the levels of ATP present by employing a luciferase-luciferin assaying reaction. A properly conducted luciferase-luciferin reaction will produce detectable and measurable levels of luminescent emissionsxe2x80x94even with relatively small quantities of analyte (e.g., down to 1 femtomole, or fm). However, it must be understood that the level of luminescent emissions generated by such assaying reactions may be quite low. For example, such levels of emissions may be as low as a fraction of a pico-watt. The measurement of levels of emission this low necessitates sensitive, efficient, and accurate detecting and measuring systems that include low noise and generally a number of specialized components.
There are many assaying and xe2x80x98luminometerxe2x80x99 systems known and available that employ photomultiplier tubes (PMTs) and cooled charge-coupled devices (CCDs) to measure low level emissions produced by bioluminescent and chemiluminescent assaying reactions. However, when considering PMT based devices, their cost is relatively high, and they may be easily damaged by shock and vibration. Further, as these devices require a high voltage supply and temperature stabilization for proper calibrated operation, they are rarely employed in low cost, low power, highly portable instruments. CCD based devices can also be expensive, especially when structured to provide the necessary sensitivity. In addition, they are generally considered to have dark noise levels that are too high for low level luminescent emission measurements, say at a xe2x80x98subxe2x80x99 pico-watt level or less. As a consequence, when CCD devices are employed, they are almost always operated at a cooled, controlled temperature (which is generally well below the ambient temperature).
Alternative and generally low cost photo-sensing devices may be found in a number of solid-state (semiconductor) photodetectors including avalanche photodiodes, silicon-carbide photodiodes, PIN photodiodes, etc. Avalanche photodiodes, which are typically operated in a photo-conductive mode, have excellent bandwidth characteristics and good sensitivity. However, as with many CCD devices, they exhibit a xe2x80x98dark currentxe2x80x99 that is generally considered too high for very low level luminescent measurements. Avalanche-photodiodes are also more expensive than other semi-conductor photodiodes, and as with PMTs, are often cooled to reduce their dark current noise levels. Other solid-state photodiodes, for example Silicon-carbide photodiodes, are not appropriate for ATP assay measurements as they have a peak sensitivity in the ultraviolet spectrum, say in the range of 200 to 380 nano-meters. PIN photodiode detectors have generally not been considered to be sensitive enough to use in low level ATP assaying luminometers. Indeed, it has generally been accepted that semiconductor diodes, including PIN diodes, are simply not suitable for such applications. This is indicated by the fact that photomultiplier tube (PMT) devices, as well as CCD based systems, have been used almost exclusively in luminometers to measure low level luminescent emissions.
Assaying arrangements that employ bioluminescent (ATP) assaying reactions to produce low levels of luminescent emissions require a means to collect a specimen or sample. Once a sample has been collected (say with a cotton tipped swab), the sample is assayed by exposure to suitable reagents and enzymes to cause the luminescent emissions-producing reaction to occur. The art provides many examples of luminometer apparatus that are employable in a lab or testing facility to measure emissions of an assaying reaction. However, these assaying arrangements are not provided in self-contained and highly portable architectures structured for the xe2x80x9cefficient detectingxe2x80x9d of such low-levels of luminescent emissions. Therefore, such systems have not been usable in the field, for example, if a cleanliness or hygiene inspection is being conducted in a hospital operating room or in a restaurant""s kitchen. In addition, known swabbing structures and associated assaying arrangements do not provide simple, self-contained, and efficient structures to collect a sample of analyte, initiate an assaying reaction in a light-tight environment, and sense and quantify the low levels of luminescent emissions associated therewith.
Accordingly, skilled persons will recognize the need for improved low level, self-contained and highly portable assaying apparatus, and associated (efficient) swabbing arrangements and structures. A most preferred apparatus and or swabbing structure would enable specimens to be collected, provide a suitable light-tight assaying environment (i.e., enclosure), include required chemical and biological materials to initiate the assaying reaction, and further enable or; support the quantifying of the low level luminescent emissions produced by the assaying reaction. A full understanding of the present invention, including an understanding of a number of capabilities, characteristics, and associated novel features, will result from a careful review of the description and figures of the embodiments provided herein. Attention is called to the fact, however, that the drawings and descriptions are illustrative only. Variations and alternate embodiments are contemplated as being part of the invention, limited only by the scope of the appended claims.
In accordance with the present invention swabbing structures, and methods of use, are provided for collecting analyte from a test surface and supporting a quantitative determination of the presence of the collected analyte. A preferred swabbing structure is configured to enable analyte to be collected upon a first surface of the swabbing pad, and subsequently detect and quantify low level luminescent emissions from (a vantage point of) a second surface or side of the swabbing pad.
In addition, preferred embodiments of the swabbing structure include a pre-wetted swabbing pad having the first surface and the second surface. Although the swabbing pad may be substantially flattened, other shapes including xe2x80x98swab shapedxe2x80x99 and xe2x80x98wedge shapedxe2x80x99 are also contemplated. Regardless of the actual shape of the (first surface of the) swabbing pad, the first surface is configured for contacting the test surface to collect available analyte located thereupon. A substantially flattened, highly porous, support and reading pad may also be provided having a first surface fixed to the second surface of the swabbing pad. The first surface of the support and reading pad, therefore, is substantially superposed by the second surface of the swabbing pad, with the support and reading pad acting, at least in part, as a physical base or support for the swabbing pad. A second surface of the support and reading pad is contemplated to provide an efficient vantage point from which to detect and quantify the low level luminescent emissions.
In addition to the swabbing pad, and the support and reading pad, a means to support the support and reading pad, and or the swabbing pad is included to enable the swabbing of the test surface and subsequently facilitate the detecting, in a light-tight environment, of any low level luminescent emissions. The emissions may be detected from the second side of the swabbing pad, or if included, a second side of support and reading pad. A movable structure is further included having fixed thereto a porous pad, or an equivalent structure. The porous pad is impregnated with suitable dried reagents that may be delivered to the swabbing pad, and other pads, when the movable structure is moved to bring the porous pad into pressure contact with the first surface of the pre-wetted swabbing pad (within the light-tight environment). As will be discussed in great detail below, the pressure contacting of the porous pad and the swabbing pad causes at least a partial compressing of the swabbing pad, which in turn causes the wetting, activating, and drawing of the (dried) reagents of the porous pad into the swabbing pad (and possibly other included absorbent, porous pads and structures). If suitable quantities of analyte have been collected by the swabbing of the test surface, an assaying reaction results that produces the low level luminescent emissions. Importantly, due to the xe2x80x98reflective porosityxe2x80x99 of structures such as the swabbing pad, and the support and reading pad, emissions produced upon or near these structures, may be efficiently sensed by placing a photo detection means (e.g., a suitable photodiode) in a suitable position proximate to the second surface of the swabbing pad, or the support and reading pad, if included.
The invention further discloses preferred methods for swabbing a test surface in order to collect and quantitatively indicate the presence of an analyte. The methods commence with the swabbing of the test surface with a pre-wetted swabbing pad. As discussed, a first surface of the swabbing pad is suitably shaped and configured for contacting the test surface to collect any available analyte. Next, the first surface of the swabbing pad is brought into pressure contact with suitable dried reagents in a light-tight environment, possibly causing the detectable low level luminescent reaction (if sufficient analyte has been collected). The efficient detecting and quantifying of the low level luminescent emissions may be made by a suitable luminometer or an equivalent instrument. Importantly, the most preferred embodiments of the methods of the present invention, provide for the collecting of analyte upon the first surface of a swabbing pad with reading and detecting of luminescent emissions being made from a second side (or surface) of the swabbing pad (possibly via the support and reading pad).